The preparation of cyclopentadiene compounds from various starting materials is well known. Metal complexes containing cyclopentadienyl or substituted cyclopentadienyl ligands are also well known. Several techniques for preparing such ligands are disclosed in U.S. Pat. No. 5,703,187, 4,985,576, 5,646,083, 5,597,935, and EP-A-563365. In copending application Ser. No. 08/122958, filed Jul. 27, 1998, the preparation of certain 1 H-cyclopenta(/)ophenanthrene containing metal complexes and their use in addition polymerization catalyst compositions is disclosed and claimed. The technique for preparing such complexes disclosed by the reference started with 1H-cyclopenta-(I)phenanthrene. In JACS, 78, 2547-2551 (1956), a synthetic scheme for preparing 1H-cyclopenta(I)phenanthrene, the ultimate step involving dehydration of 2,3-dihydro-2-oxo-1H-cyclopenta(I)phenanthrene with boric acid was disclosed. Disadvantageously, this particular procedure resulted in low yields and insufficient purity of the resulting ligand group containing compounds.
Previously known synthetic procedures involved multiple unit operations, thereby making the process less efficient than desired. Accordingly, it would be desirable if there were provided a process for preparing 4-ketocyclopentene or substituted 4-ketocyclopentene compounds and cyclopentadiene or substituted cyclopentadiene derivatives thereof in higher yields and purity.